Recent developments have focused on ultrawideband (UWB) communication and UWB radar and various techniques have been developed. For example, UWB communication transfer rates have been improved so that as the pulse time width becomes smaller, the bandwidth can be made correspondingly wider.
Methods using short pulses as a signal source or methods of using a burst oscillation circuit have been adopted to achieve this type of UWB communication and UWB radar. For example, methods using a burst oscillation circuit involve controlling the ON/OFF of the burst oscillation circuit in response to burst control signals to oscillate the burst oscillation circuit for only certain time periods to generate burst oscillation signals.
Conventionally, various types of pulse generators have been considered for adoption in UWB communication and UWB radar.
Japanese Laid-open Patent Publication No. 2007-174087 and Tuan-Anh Phan et al., “A 18-pJ/Pulse OOK CMOS Transmitter for Multiband UWB Impulse Radio,” IEEE Microwave and Wireless Components Letters, Vol. 17, No. 9, September 2007 are examples of the related technology.
As described above, a pulse generator adopted for UWB communication and UWB radar is used to control the ON/OFF of a burst oscillation circuit in response to burst control signals.
Specifically, a transistor switch is provided between differential terminals of a burst oscillation circuit (differential amplification circuit). When the level of a burst control signal is high (H), a switch is turned OFF (oscillating state), and when the level is low (L), the switch is turned ON (oscillation stopped).
However, a delay is caused in the period of time from switching the transistor from ON to OFF until oscillation actually starts, that is, the time until the oscillation rises in the abovementioned pulse generator.
This time delay until the rise of oscillation is a serious problem in UWB communication and UWB radar using pulse signals (carriers) in the range of several tens of GHz (e.g., 60 to 90 GHz).